Preparation, morphology, crystal structure, energy gap and photoluminescence studies of Mn2+/Cr3+ doped ZnS quantum dots

Abstract

Mn added ZnS (Zn0.97Mn0.03S) and Mn-Cr doped ZnS (Zn0.95Mn0.03Cr0.02S) nanostructures were synthesized by co-precipitation process. X-ray diffraction analysis confirmed the cubic phase with highest intensity along (111) orientation. The shrinkage of crystallite size from 36 Å (Zn0.97Mn0.03S) to 26 Å (Zn0.95Mn0.03Cr0.02S) and the influence of Cr and Mn on morphology, optical and photoluminescence characters in ZnS were investigated. The substitution of Cr in Zn-Mn-S lattice not only diminished the crystallite size and also produced more defect associated luminescent activation centres. The presence of Zn2+, Mn2+ and Cr3+ ions in Zn-Mn-Cr-S lattice was confirmed by XPS spectra. The elevation in energy gap by Cr addition was explained by Burstein–Moss effect and reduced crystallite size. The tuning of energy gap as well crystallite size of basic ZnS nanostructure by Mn/Cr substitution encourages these materials for modern electronic applications. FTIR spectra established the occurrence of Mn/Cr in Zn-S lattice by their characteristic bondings. The inclusion of Mn /Cr provides an efficient control over modification of various emissions which suggests their applications in organic light emitting diode materials.